Re: Need help with PI PICO...

On 30/03/2024 09:17, The Natural Philosopher wrote:

On 30/03/2024 02:04, Jim H wrote:

On Fri, 29 Mar 2024 10:49:13 +0000, in <uu66b9$83pi$3@dont-email.me>,
The Natural Philosopher <tnp@invalid.invalid> wrote:
>

Maybe ascii art will help
>
CONTROL=10µs
____| |________
>
RETURN = wahatever
_____|^^^^^^^^^^^^|____________
>

>
Assuming my bleary-eyed math is correct, 10µs is the length of one
cycle of ultrasound at 100,000 Hz.
>

The width of that pulse is pretty much immaterial - its only a digital trigger, It doesn't send anything directly.
 The unit does that, and senses a high to the output. Then it transmits a squawk., When it receives an echo it switches that to low.
 Its a smart device .
 

I think that is the part I was missing. I assumed it was like an analog device, out pin was for send  and the in pin signalled it was receiving.
On reflection, the code makes sense if it is a smart device. The in pin just goes high (or low) for the period between sending and receiving a few micro seconds of the echo.

https://cdn.sparkfun.com/datasheets/Sensors/Proximity/HCSR04.pdf
 

Not the most precise wording.
Having taken the trouble to understand. I might buy one to tell me if my garage door is open. Buy an echo device that is, not a PICO.